The present invention relates in general to electronic measuring devices, and in particular to a new and useful capacitive length and/or angle measuring device, the transducer of which consists of a stationary part and a part which is displaceable parallel thereto over the surface thereof at a short distance. The opposite surface of the stationary and displaceable parts are provided with capacitor coatings.
Capactive transducers designed as differential capacitors are known. In practice, however, difficulties arise especially when measuring relatively great lengths with such known differential capacitors. To eliminate such difficulties, according to Swiss Patent 539,837 several differential capacitors are arranged one behind the other in a capacitive length measuring device. If in the displacement the measurement range of this differential capacitor is exceeded, expensive circuitry is needed to connect the differential capacitor next following in the direction of displacement to the electronic circuit device. In this system, the position information is contained in the amplitude of the feed voltages of the differential capacitor.
From German OS 28 53 142 a measuring device for capacitive determination of the relative positions of two mutually movable parts is further known, consisting essentially of a sliding piece and a scale. A phase angle .phi. of the receiver voltage is a linear function of the displacement of the sliding piece relative to the scale, if the transmitting voltages have sinusoidal form.
A disadvantage of this is that due to the small overlap between the transmitting electrodes and the scale electrodes the amplitude of the received signal is small. Another disadvantage is that the scale electrodes have a semi-sinusoidal form and therefore are difficult to produce with the necessary precision.